Siding panels for building structures are traditionally made from either extrusions, in which case the siding panel typically does not include surface variations, or by injection molding, which permits molding of panels with many shapes and contours.
One of the limitations on injection molding of panels is the ability to remove the panels from the mold after the injection molding is complete. Most injection molds for siding are designed so that the molded panel can be easily ejected from the mold. Thus, such molds are generally fixed in shape and do not include many moving parts. However, fixed molds inhibit the ability to incorporate curved undercut components into panels, including mounting rails.
In previous methods for forming siding, rails have been formed on the front side of a siding panel by various methods, including folding the panel over on itself at the upper end, extruding the panel with the rail, or molding the rail as a separate piece and then affixing the separately molded rail to the panel. Most commonly, panels are manufactured with interrupted rail segments are used since they can be more readily fabricated. However, most contractors would prefer a continuous rail in order to facilitate installation.